This invention concerns a system of electrical thermostatation of pipes for the transport of fluid and semi-fluid products. Furthermore, this invention is referred to the possibility of maintaining the temperature (heating) of a process fluid transported by means of piping or kept in a tank.
It is well known to the state of technology that, in many production processes of the chemical and foodstuff industries and similar, it is necessary to keep the product at a constant temperature, throughout the transfer or piping process, in order to guarantee the conservation of its properties, in particular the degree of viscosity, in such way as to make transport by means of channelling into pipes, possible and economical.
In the current situation thermostatation of process piping is obtained by means of lagged piping, made up of two concentric pipes that create a cavity through which the thermovector fluid may be passed. This solution is made through the assembly of mechanical components (pipes, bends, bottoms) joined by means of fixed welded joints.
One observes that this technique of thermostatation may provoke, in certain cases, contamination of the process fluid by the thermovector fluid, due to any possible cracks or corrosions of the process piping. This is an eventuality that is particularly hazardous in all the fields of application possible in the chemical field, reactions being possible between the two fluids with the possibility of the bursting of the pipe itself; in the pharmaceutical and foodstuff fields, contamination being possible which makes the product transported hazardous and unusable.
Such risk may be reduced, taking preventive actions such as for instance continual quality controls and frequent maintenance of plant and equipment. However, such actions determine greater complexity of the production processes and a subsequent increase in costs.
Furthermore, in case of accidental breakage of a pipe, it may be difficult to identify the position, with subsequent high costs to be added to those relative to the loss of the product.
These well known systems may also generate lack of homogeneity on the transversal cross section of the flow of thermovector fluid inside the cavity, due to the setting up of preferential flows of this fluid and, subsequently, a non uniform distribution of the temperatures on the exchange surface between the thermostating fluid and the thermostatised one. This inconvenience is exalted by the superficial state of the area of heat exchange; deposits and incrustations accentuate the lack of homogeneity of the heat distribution. Furthermore, the insulation of the external pipe of the cavity may be difficult, this being created on “site”: not very practical technology, especially for the pharmaceutical and foodstuff industries, where the process piping and thermostatisation need frequent interventions and movements due to operative and productive needs.
Finally, such techniques require the use of superior materials such as stainless steel with low carbon content and high resistance to corrosion.
The issues listed above are currently overcome by creating a system that is able to annul the risk of pollution between the thermostatising fluid and the product, consisting of a heating element travelled over by a circuit of thermovector fluid completely independent from the process circuit. This solution may mean certain inconveniences in case the pipes are to be installed in an external environment at low temperatures, in a particular way when one envisages the use of water as the thermovector fluid and the piping has a discontinuous functioning. Indeed, these possibilities mean the maintaining in functioning of the thermovector circuit to avoid phenomena of freezing. Systems of this type use an electrical tracing of the process pipe in particular creating a direct placing of an electrical heating element alongside the piping. Due to the limited extension of the contact surface between the heating element and the process piping, the exchange rendering is reduced and therefore, in order to obtain the same useful effect, it is necessary to envisage high temperatures in the heating element. Inevitably, high localised temperatures generate lack of homogeneity of the temperatures along the transversal cross section of the process pipe with peaks in correspondence with the point of contact.
This distribution of the temperatures may be incompatible with the peculiar characteristics of the product, especially in the pharmaceutical and foodstuff field.